A very confusing cursor when sculpting
The center colored dot snaps to the nearest vertex and also appears on the other side of the model if you have mirroring turned on, as Yohello said. As far as I can tell, the outer circle shows the size of the brush, and the inner circle represents the strength / falloff of the brush, and increases in size as you increase the brush strength.

If you want to disable the cursor entirely, you can uncheck the "cursor" box on the right panel. If you do this, There will only be the normal mouse icon to show the cursor position until you click the mouse / press down the tablet pen to begin sculpting, at which point there will be no cursor.

Or, you could go to the cursor color settings and change the cursor alpha to 0, and a simple crosshair will be shown at all times instead of the dot and circles. Hope this helps!